Radio signaling circuit



Aug. 24, 1948. HINGS 2,447,701

RADIO SIGNALING CIRCUIT Filed March 2'7, 1943 POWER SL1 PPL MODU LAT! ON I NVENTOFZ DONALD L. H l N63 ATTORN :Ys

iatented Aug. 24, 1948 U lr'ii S Flfi E RADIO SIGNALING Jomomr Donald L. Hings, Ottawa, Ontario; Canada; assignor to ElectronicLaboratories;Inc;, Indianapolis, 1nd; at corporation of Indiana" Application March 27, 1943, Serial No. 480,766 In Canada March 22,1943

17 Claims.

My invention relates-in general to radio ire-- trol elements for the-high frequency system, or-

wherein other elements are coupled to the oathodes to givea combined action;

Another object of -my invention is to obtain high efficiency with a'minimum of distortion.

Another object is to amplitude modulate'radio frequency with the control grids andshieldsas control elements for the low frequencies- Another object is to neutralize the'phase displacement of one tube by that of the other.

Another object is to rendermyinvention highly efiicient by reducing the modulation requirements.

Another object of my invention is to operate an amplifying tube in-such am'anner that fan additive negative cycleexists' on the 'cathodeinaddition to the constant radio' frequency potentialsapplied to the cathode drive circuit.

Another objectof my invention is to operate an amplifying tube insuch a manner thata positive cycle' or a portion ofa positive-cycle exists on the plate in addition to the constant potentials on the plate substantially concurrently with the existence of the said additive negative cycle on the cathode;

Another object :of my invention i to operate the control grids or elements of an amplifying tube as valves, and avoid their carrying radio frequency energy.

Another object ofmy invention'is to obviate- The figure shows a schematic diagram of my circuit and may be characterized asahighlyefficient amplitude modulated amplifier-system.

to operate two A My inventioncomprisesgenerally a carrier=wave= input resonant circuit indicated generally by the Nil -171.5)

2 reference characters l 2 tube 6;a radio frequencyoutput resonant-circuit 14} I5, and I6, two push-pull modulated amplifying tubes 3! and 31, a modulation input transformer 26; and-an output load circuit 41,-

The carrier wave input circuit l, 2 andl is coupled to the control grid 9 of the radio frequency amplifying tube 6=bya grid coupling condenser 3. Thescreen grid 8 is connected to the power supply-54throughadropping resistance [2 and isby-paSSed to-ground'by the capacitor II. The cathode-lllis connectedtoground. Th plate 1 is connected to the output resonant circuit 14,-

i5 and I6.- A plate radiofrequency choke I3 is connected between-the power supply 5| and the plate I and prevents radio frequency from entering thepower supply; The output resonant circuit'lt, I5 and iii-'maybe characterized as'a double-ended l circuit,in that the center portion ofthe inductance I6 is maintamedsubstantially at"-ground*potential. Thus'the energy delivered tome-amplifying tube 3i through the coupling condenser I1 is substantiallydegrees out of phase -tothe radio frequency energy delivered to the amplifying tube 31 through the coupling condenser l 8.

In my "invention I apply the radio frequency energy from'the'coupling condenser I! to both the"cathode 36-and the screen or accelerating grid 34*01' the tube 3!,

pliedtoboth the cathode 42 and the screenor accelerating grid 40 of the tube 31' As illus -trated,- the screen or accelerating grid 34 of the tube 3l" is connectcd'to the cathode 36 through a high'frequency coupling condenser 20 and the screenor accelerating grid 4!! 'of the tube 31 1s coupledto the cathode through a high frequency couplingvcondenser 19. The coupling of thescreen grid to the cathode is to prevent electron flow'in the tube between the cathode and screen gridat-radio frequencies which would normally-tend to flowinstantaneously to the cathode tending to swing away from the screen grid if the screen grid were maintainedat a fixed potential. In other-Words, in my invention the screen grid swings with the cathode with the result'that less radio frequencyenergy is required to efliciently-drive the cathode circuit; This arrangement-tends to reduce distortion; The cathodes 36* andare connected to ground respectively througlrhigh frequency filter chokes 24 and- 23 to preventthe radio frequency from flowing to groundy'thusmaintaining the cathodes at high and 4, and amplifying Similarly the radio fre-- quency from the coupling condenser I8 is sup:

tively by the reference characters 33 and 39, are 7 also connected to the modulation input transformer 26. plates and associated shields are biased with the control grids and thus will not attract electrons that are emitted by the cathodes. This arrangement not only reduces the load on the cathode but also prevents distortion. The lower end of the secondary of the modulation input transformer 26, is connected to a bias source 55 and is maintained at a fixed potential through the low frequency by-pass condenser 46,

The terminals of the output resonant load circuit 41, 48 and 45 and are coupled respectively to the plates 32 and 38 of the tubes 3| and 31 by coupling condensers 44 and 45. The load circuit may be tuned to resonance by operating the inductances 49 and 50 and the condensers 41 and 48. The resonant load arrangement is doubleeended for push-pull operation.

The system so far described is completely operative for delivering output energy to the load with good linear modulation response. However in order to prevent saturation of the screen grids 34 and 40 at excessive modulation peaks, I arrange for feeding back inversely a small portion of the modulation energy from the plates 32 and 38 to the screen grids 34 and 40. This inverse feed-back arrangement comprises generally an inverse feed-back transformer which has its primary connected to the plates 32 and 38 through high frequency chokes and 25 respectively and which has its secondary connected to the screen grids 34 and 40 through high frequency filter chokes 2| and 22 respectively, thus delivering modulation energy to the screen grids.

The lower end of the primary of the inverse feed-backtransformer 25 is connected to a power supply 56 and the lower end of the secondary is maintained at a fixed potential by the condenser 28. The resistor 21 is a current limiting resistance for the screen grids 34 and 4B.

. In operation stable radio frequency is applied to the terminals of the input inductance and, in turn is impressed upon the control grid 9 Which is connected to ground through a resistor 5, and which governs the operation of the high frequency amplifying tube 6. The amplified energy from the tube 6 is delivered to the doubleended output resonant circuit l4, l5 and I6, from which opposite phase energy is fed to the cathodes and the screen or accelerating grids of the two tubes 3| and 3'! of the push-pull amplifier arrangement. Modulation is applied to both the control grids 35 and 4| and the beam-forming plates and accompanying shields 33 and 39. Under modulation, the two tubes 3| and 31 deliver modulated energy to the double-ended output resonant circuit 41, 48 and 49 and thereupon to the load across the terminals of the inductance 5. Under excessive conditions of modulation the inverse feed-back transformer arrangement is effective to reduce distortion which would tend to occur from overload.

With the tubes 3| and 31 operating in a push- In this manner the beam-forming pull arrangement and with the cathodes and the screen grid driven by radio frequency energy and with the control grid and the beam-forming plates and the associated parts by-passed to ground for radio frequency, I am able to obtain a high efficient operating condition wherein the radio frequency drive voltage can be considered additive on the negative cycle to the constant radio frequency potentials applied to the cathode drive circuit. The additive negative cycle on the cathode of one tube is the operative cycle of the tube and the opposite cycle is the operative cycleof the other tube. This means that I am able to add the full radio frequency drive voltage to the constant radio frequency potentials applied to the cathode, thereby producin a greater peak modulation. During this cathode negative cycle, the grid will be positive and maximum electrons will be emitted from the emitting elements of the tubes. As the screen grid is also negative a minimum of electrons will be received by it. This arrangement is unique; in that, the input and output circuits of the tube, as well as the control elements may be arranged such that while the additive negative cycle on the cathode exists there concurrently exists an additive positive cycle upon the plate to the constant potential on the plate. The additive positive cycle may be substantially in alignment with the negative additive cycle on the cathode or they may be shifted with respect to each other, so that additive negative energy is existing on the cathode while additive positive energy exists upon the plates. In any event there may exist, at least a portion of or substantially all of the additive positive cycle with respect to the additive negative cycle to Produce an effectively greater amplitude of voltage on the tube for modulation requirements.

In addition to having a highly efficient amplifier tube system I am able to obtain a good linear response because the grid and the beam-forming plate parts merely act as valves and do not carry any radio frequency energy. In my general pushpull arrangement, since the control grid and beam-forming plate parts are by-passed to ground for radio frequency, there is no need for neutralizing the circuit for radio frequencies.

Although I have shown and described my invention with a certain degree of particularity, it is understood that changes may be made therein without departing from the spirit of the invention which are included within the scope of claims hereinafter set forth.

I claim as my invention:

1. A radio frequency transmitting system comprising at least two amplifying tube connected in a push-pull arrangement, each said tube having a cathode, a control element, an accelerating grid and a plate. a sourceof carrier wave potentials applied to the cathode of each amplifying tube with at least part of the plate-tocathode carrier current of the amplifying tubes flowing through the source of carrier Wave potentials, the control element of each amplifying tube being by-passed to ground for carrier wave frequency, the plate of each tube being connected to a resonant output load circuit, and means for applying modulating potentials to the control element of each amplifying tube, the accelerating grid of each amplifying tube being coupled to the cathode.

2. A radio frequency transmitting system comprising at least two amplifying tubes connected in a push-pull arrangement, each said tube having. acathode-a control element, an accelerate ing grid and a plate, .a'source of carrier wawepc tentials applied to the cathode of each amplifying tube with at least part. of the plateto-cathode carrier current of the amplifying tubes flowing through the source of carrier wave potentials,

thecontrol element of each amplifying tube being ode, an inverse feed-back means for-feeding a small portion of the modulated energy to celerating grids.

the ac- 3. A radio frequency transmittingsystem com-- prising at least-two amplifying tubes of the beam type connected in a'push-pul} arrangement, each said tube having a cathode, a controlelement,

an acceleratin grid, beam-forming parts, and a plate, a source of carrier wave potentials applied to the: cathode of each amplifying tube with at least part of the plate-to-cathode carrier current of the amplifying tubes flowing through the source of carrier wave potentials, the control element of each amplifying tube being by-passed to ground forcarrierwave frequency, the plate of each tube being connected to a resonant output load circuit, and means for' applying modulating potentials to'the control element of each amplifying tube, the accelerating grid of each amplifying tube being coupled tothe cathode,

the source of carrier wave potentials, a source of modulating potentials applied to the control element, said amplifying tube having an accelerating grid coupled to the cathode, and inverse feed-back means for feeding a small portionof the modulated energy to the accelerating grid.

5. In aradio frequency system comprising a driven amplifying tube having a, plate circuit including a cathode, a source of-carrier wave potentials including a driving amplifying tube having a plate circuit including a plate, an impedance element common to both plate circuits, whereby the driven amplifying tube reflects a varying impedance in the plate circuit of the driving amplifying tube, said impedance element being connected between the cathode of the driven tube and ground and between the plate of the driving tube and ground, said driven tube having control means, and a source of modulating potentials applied to the control means.

6. A radio frequency system comprising at least two amplifying tubes connected in a pushpull arrangement, said tubes each including a cathode and a plate, a source of carrier wave poin a push-pull arrangement, said tubes each having a cathode, afirst control. element, a second control. element anda plate, a source of carrier wave potentialsfor exciting the cathode of each amplifying tube with respect to a point of reference potentiaL-thefirst control element of each amplifying tubebeing by-passed to the said point of reference potential for carrier wave frequency, a resonant output-load circuit connected to the plate -of each tube, means for applying modulating. potentials to the first control element of each tube, the second control element of each amplifying tubebeing coupled to the cathode, and inprising at least two amplifying tubes connected in a push-pull arrangement, said tubes each having a cathode, a first control element, a second control. element and a plate, a source of carrier wave potentials forexciting the cathode of each amplifying tube with respect to a point of reference potential, the first control element of each amplifying tube being by-passed to the said point of reference potential for carrier wave frequency, a resonant output load circuit connected to the plate of each. tube, means for applying modulating'potentials to the first control element of each tube, the second control element of each amplifying tube being coupled to the cathode, and means receiving energy from the plate for feeding aportion of the modulated energy to the second control element. V

w, 9. A radio frequency system comprising an impedance element, a space discharge tube including an electron discharge path; a resonant load circuit, means to effectively connect in series said impedance element, electron discharge path,

and resonant load circuit, meansfto supply carrier waveenergy across the impedance element,

modula-ting means formodulating the carrier wave output of said tube, said space discharge tube having a cathode and a control element,

said cathodebeing grounded through said carrier wave supply means, and means connected to charge path, said tube having acathode and output electrode means, a load circuit connected to the output electrode means, means to supply carrier wave energy to said cathode, said cathode being grounded through said carrier wave sup-v ply means, said tube having a first control electrode, means for applying modulating potentials to said first control electrode and thereby controlling said tube for supplying modulated energy to the load circuit, said tube having a second control electrode, and means connected to the load circuit for feeding modulated energy to said second control electrode.

11. A radio frequency system comprising an amplifying tube having a cathode, a first control element and a plate, a source of carrier wave potentials for exciting the cathode with respect to a point of reference potential, said cathode being grounded through said source of carrier wave potentials, means for applying modulating potentials to the first control element, said amplifying tube having a second control element coupled to the cathode, and means receiving energy from the plate for feeding a portion of the modulated energy to the second control element.

7 12. A radio frequency system comprising an amplifying tube having acatho-de, a first control element and a plate, a source of carrier wave potentials for exciting the cathode with'respect -to a point of reference potential, said cathode being grounded through said source of carrier wave potentials, means for applying modulating potentials to the first control element, said amplifying tube having a second control element,

and inversefeedback means for applying energy from said plate to said second control element.

. 13. A radio frequency system comprising at least two amplifying tubes connected in a pushpull arrangement, said tubes each having output electrode means, a load circuit connected to the output electrode means of each tube, high frequency choke means connected across said load circuit, said choke means having a center-tap,

a transformer connected between said center- :tap and a point of reference potential to receive driven amplifying tube having a plate circuit including a cathode, a source of carrier wave potentials including a driving amplifying tube having a plate circuit including a plate, an impedance element common to both plate circuits, whereby the driven amplifying tube reflect a varying impedance in the plate circuit of the driving amplifying tube, said impedance element being connected between the cathode of the driven tube and ground and between the plate of the driving tube and ground, said driven tube having control means, a source of modulating potentials applied to the control means, and inverse feedback means for feeding a portion. of the modulated energy to the control means.

15. In a radio frequency system comprising a driven amplifying tube having a plate circuit including a cathode, a source of carrier vwavepotentials including a driving amplifying tube having a plate circuit including a plate, an impedance element'common to both plate circuits, whereby the driven amplifying tubeirefiects a varying impedance in the plate circuit of the driving amplifying tube, said impedance element being connected between the cathode of the driven tube and ground and between the plate of the driving tube and ground, said driven tube having first and second control means, a source of modulating potentials applied to the first. control means, and inverse'feed-back means for feeding a portion of the modulated energy to the second control means.

- 16. A radio frequency system comprising at least two amplifying tubes connected in a pushpull arrangement, said tubes each having output electrode means, a load circuit connected to the output electrode means of each tube, high frequency choke means connected across said load circuit, said choke means having a center-tap,

a transformer connected between said centertap and a point of reference potential to receive energy from said load circuit, said amplifying tubes each having first and second control means, a source of modulating potentials applied to the first control means, and connection means for connecting the transformer to the second control means of each tube for energizing the said second control means.

1'7. A radio frequency system comprising an impedance element, a space discharge tube including an electron discharge path, a resonant load circuit, means to effectively connect in series said impedance element, electron discharge path, and resonant load circuit, means to supply carrier wave energy across the impedance element, said space discharge tube having a cathode and a control element, condenser means connected between said cathodeand said controlelement, and means connected to the load circuit for feeding energy from the load to the control element.

DONALD L. HINGS.

REFERENCES CITED The following references are of'record in the file of this patent UN ITED- STATES PATENTS Number Name Date 1,999,190 Hansell Apr. 30, 1935 2,002,209 Nordahl May 21, 1935 2,008,996 Suydam July 23, 1935 2,053,414 Barden Sept, 8, 1936 2,101,438 'Lindenblad Dec. 7, 1937 2,298,629 Schaper Oct, 13, 1942 FOREIGN PATENTS I Number Country Date 443,803 Great Britain Mar. 6, 1936 

